Tasmania is the most important tin province in Australia, having been endowed with >0.65 Mt Sn. Some granitic intrusions in western Tasmania have distinctive tourmaline- and quartz-rich magmatic-hydrothermal features, whether they are mineralized (e.g., Heemskirk Granite) or barren (Pieman Heads Granite). The Devonian Heemskirk and Pieman Heads plutons crop out on the western coast of Tasmania and are characterized by similar mineralogical and geochemical compositions and ages. The magmatic-hydrothermal textural features include tourmaline patches, tourmaline orbicules, and tourmaline-muscovite veins, as well as miarolitic cavities and quartz-fluorite-sulfide veins in the Heemskirk Granite. Cathodoluminescence (CL) imaging, laser ablation-inductively coupled plasma-mass spectrometry, and microthermometric analyses of quartz have revealed the physicochemical evolution of the magmatic-hydrothermal fluids from which these tourmaline- and quartz-bearing assemblages precipitated. High Ti quartz (20–28 ppm) in tourmaline patches, orbicules, and cavities typically have homogeneous CL-bright intensity, whereas CL-dark fractures have cut and/or offset the CL-bright and -gray domains that characterize low Ti quartz (3.4–8.5 ppm) from the tourmaline veins. The earliest fluid inclusion assemblages in the quartz-tourmaline orbicules and cavities have a salinity range from 3 to 14 wt % NaCl equiv with intermediate density and were probably trapped at lithostatic pressures of 1.57 ± 0.2 kbar and temperatures of 550° to 570°C, suggesting a depth of 5.9 ± 0.8 km. Prolonged depressurization and cooling may have led to the evolution of a brine (~39 wt % NaCl equiv salinity) from the primary magmatic liquid, which formed halite-bearing hypersaline inclusions in the tourmaline orbicules. Continuous pressure decrease explains the intense brittle failure and fluid migration outward from the apical portions of the pluton, where magmatic fluids partially mixed with and were cooled by external meteoric water. These mechanisms triggered the formation of tourmaline-muscovite-quartz veins and local cassiterite-bearing greisens from a moderate-salinity fluid (~12 wt % NaCl equiv) at temperatures of ~300°C and hydrostatic pressures of 120 bars. Retrograde dissolution textures evident from CL-bright quartz cores surrounded by oscillatory growth zones with gray CL response characterize the low Ti (<1 ppm) and high Al (500–1,000 ppm) quartz from the fluorite-sulfide veins that precipitated from a low-salinity (5.7 wt % NaCl equiv) acidic fluid at temperatures of 200° ± 25°C and hydrostatic pressures of <50 bars. High Sb concentrations (up to 80 ppm) in quartz may be an indicator of low-temperature base metal mineralization related to granitic intrusions. Abundant fluid percolation, protracted fractional crystallization, and high tin concentrations in exsolved hydrothermal fluids may explain why the Heemskirk Granite is well endowed in Sn and base metal deposits, whereas the Pieman Heads Granite is barren.

中文翻译：

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澳大利亚东南部含锡矿化和贫瘠塔斯马尼亚侵入体中岩浆热液特征的形成：石英质地、微量元素和微量测温法的见解

塔斯马尼亚是澳大利亚最重要的锡产区，拥有超过 0.65 Mt 的锡。塔斯马尼亚西部的一些花岗岩侵入体具有独特的富含碧玺和石英的岩浆热液特征，无论它们是矿化的（例如 Heemskirk Granite）还是贫瘠的（Pieman Heads Granite）。泥盆纪 Heemskirk 和 Pieman Heads 岩体在塔斯马尼亚西海岸出没，具有相似的矿物学和地球化学成分和年龄。岩浆-热液构造特征包括电气石斑块、电气石球状体和电气石-白云母脉，以及Heemskirk花岗岩中的微晶洞和石英-萤石-硫化物脉。阴极发光 (CL) 成像、激光烧蚀电感耦合等离子体质谱法、石英的显微测温分析揭示了岩浆-热液流体的物理化学演化，这些含电气石和石英的组合从中沉淀出来。电气石斑块、球状体和空腔中的高 Ti 石英（20-28 ppm）通常具有均匀的 CL 亮强度，而 CL 暗裂缝切割和/或抵消了表征低 Ti 石英的 CL 亮区和灰色域（ 3.4–8.5 ppm）来自电气石脉。石英-电气石球体和空腔中最早的流体包裹体组合的盐度范围为 3 至 14 wt% NaCl 当量，具有中等密度，可能被困在 1.57 ± 0.2 kbar 的岩石静压和 550° 至 570°C 的温度下，建议深度为 5.9 ± 0.8 公里。长时间的减压和冷却可能导致从原生岩浆液体演化出盐水（~39 wt% NaCl 等效盐度），在电气石球状体中形成含岩盐的高盐度包裹体。持续的压力下降解释了剧烈的脆性破坏和流体从岩体顶部向外迁移，在那里岩浆流体与外部大气水部分混合并被外部大气水冷却。这些机制引发了在约 300°C 的温度和 120 巴的静水压力下，由中等盐度的流体（约 12 wt% NaCl 当量）形成电气石 - 白云母 - 石英脉和局部含锡石的 greisens。从 CL 明亮的石英岩芯明显的逆行溶解结构被具有灰色 CL 响应的振荡生长区包围，表征了低 Ti (< 1 ppm) 和来自萤石-硫化物脉的高铝 (500–1,000 ppm) 石英，在 200° ± 25°C 的温度和 <50 的静水压力下从低盐度（5.7 wt% NaCl 当量）酸性流体中沉淀出来酒吧。石英中的高 Sb 浓度（高达 80 ppm）可能是与花岗岩侵入体相关的低温贱金属矿化的指标。大量的流体渗流、长时间的分步结晶和溶出的热液中的高锡浓度可以解释为什么 Heemskirk 花岗岩富含锡和贱金属矿床，而 Pieman Heads 花岗岩贫瘠。石英中的高 Sb 浓度（高达 80 ppm）可能是与花岗岩侵入体相关的低温贱金属矿化的指标。大量的流体渗流、长时间的分步结晶和溶出的热液中的高锡浓度可以解释为什么 Heemskirk 花岗岩富含锡和贱金属矿床，而 Pieman Heads 花岗岩贫瘠。石英中的高 Sb 浓度（高达 80 ppm）可能是与花岗岩侵入体相关的低温贱金属矿化的指标。大量的流体渗流、长时间的分步结晶和溶出的热液中的高锡浓度可以解释为什么 Heemskirk 花岗岩富含锡和贱金属矿床，而 Pieman Heads 花岗岩贫瘠。